Antiferrodistortive phase transition in EuTiO3

X-ray diffraction, dynamical mechanical analysis and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300K the perovskite structure changes from cubic Pm-3m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis (a0a0...

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Published in:arXiv.org 2012-08
Main Authors: Goian, V, Kamba, S, Pacherova, O, Drahokoupil, J, Palatinus, L, Dusek, M, Rohlicek, J, Savinov, M, Laufek, F, Schranz, W, Fuith, A, Kachlik, M, Maca, K, Shkabko, A, Sagarna, L, Weidenkaff, A, Belik, A A
Format: Article
Language:English
Subjects:
Brillouin zones
Ceramics
Crystal defects
Crystal structure
Diffraction
Electron diffraction
Infrared analysis
Infrared spectra
Infrared spectroscopy
Mechanical analysis
Modulation
Perovskite structure
Perovskites
Phase transitions
Reflectance
Single crystals
Strontium titanates
X-ray diffraction
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Summary:X-ray diffraction, dynamical mechanical analysis and infrared reflectivity studies revealed an antiferrodistortive phase transition in EuTiO3 ceramics. Near 300K the perovskite structure changes from cubic Pm-3m to tetragonal I4/mcm due to antiphase tilting of oxygen octahedra along the c axis (a0a0c- in Glazer notation). The phase transition is analogous to SrTiO3. However, some ceramics as well as single crystals of EuTiO3 show different infrared reflectivity spectra bringing evidence of a different crystal structure. In such samples electron diffraction revealed an incommensurate tetragonal structure with modulation wavevector q ~ 0.38 a*. Extra phonons in samples with modulated structure are activated in the IR spectra due to folding of the Brillouin zone. We propose that defects like Eu3+ and oxygen vacancies strongly influence the temperature of the phase transition to antiferrodistortive phase as well as the tendency to incommensurate modulation in EuTiO3.
ISSN:2331-8422
DOI:10.48550/arxiv.1206.4137